Plural annular coaxial combustion chambers



. April 2, 1957 LEDUC 2,787,120

PLURAL. ANNULAR COAXIAL COMBUSTION CHAMBERS Filed July 28, 1951 4 Sheets-Sheet l A ril 2, 1957 R. LEDUC ,1

PLURAL. ANNULAR COAXIAL COMBUSTION CHAMBERS Filed July 28, 1951 4Sheets-Sheet 2 April 2, 1957 R LEDUC PLURAL ANNULAR COAXIAL COMBUSTION CHAMBERS Filed July 28, 1951 4 Sheets-Sheet 3 United States Patent PLURAL ANNULAR COAXIAL COMBUSTION CHAMBERS Ren Leduc, Argenteuil, France Application July 28, 1951, Serial No. 239,083

Claims priority, application France August 5, 1950 9 Claims. (Cl. 60---39.69)

The aerodynamic resistance of a supersonic aeroplane depends mainly on the frontal surface of the machine; when the propulsive plant is constituted by thermopropulsive ducts, ram jets or the like it is therefore evidently of interest to reduce a much as possible their maximum cross section or midship frame.

On the other hand, the best efficiency in the conversion of energy is obtained, for similar ducts, by utilizing a combustion chamber of much greater cross-section than the cross-sections of the inlet and outlet of the duct. Reduction of the combustion chamber, with a view to reducing the aerodynamic resistance, leads, in consequence, to a considerable loss of energy, reflected in a decreased thrust and an increased specific fuel consumption.

The present invention has as its object a propulsion apparatus with certain improvements in thermopropulsive ducts and particularly in their combustion chamber, whereby these disadvantages are obviated.

According to one characteristic of the invention, the combustion zone is situated downstream of a zone of deflection which is oblique to the direction of the gas stream and in which the latter is deflected. This zone of deflection may be substantially conical or frusto-conical, coaxial with the duct and open to the rear.

Such a zone of deflection can be created, for instance, by deflecting blading, by injection or by suction; at supersonic speeds, the shock waves observed in these regions can be assimilated to zones of deflection according to the invention.

The presence of such an oblique zone of deflection in front of the combustion zone tends, as will be shown hereinafter in greater detail, to replace, as far as the combustion is concerned, the straight section of the duct by an oblique section, that is to increase considerably a cross-section of the combustion chamber without increasing the maximum cross-section or midship frame of the duct.

According to another characteristic of the invention, a second oblique zone of deflection is situated behind the combustion zone and substantially parallel with the first zone, for straightening out the stream lines.

The zones of deflection are then the cause for the creation of forces whose resultant is directed forwardly, that is, in a sense opposed to the direction of the air stream. It is possible in this way to obtain a total thrust on the duct approaching that which would be obtained if the cross-section of the combustion chamber were infinite. With the invention the total thrust at the outlet end of the duct is increased because of the increase in the combustion area and because of the faster fluid flow produced by the invention.

drawings, in which:

Figures 1 and 2 are schematic representations of the .arrangements of the invention.

Figure 3 is a partial schematic section of the thermo- 2 propulsive duct provided with the arrangements according to the invention.

Figure 4 illustrates details of a form of construction of the invention.

Figure 5 illustrates details of another form of construction of the invention.

Figure 6 illustrates details of another arrangement according to the invention.

Figure 7 illustrates in a cross-sectional view a structure according to the invention.

Referring to the figures in which the same reference numerals are used for corresponding elements, it will be seen that the air upstream of the combustion chamber has a velocity V1 including angle a with the zone of deflection 1. After crossing the zone of deflection, the air has a velocity V2, much smaller than V1 and directed at and angle 6 with the zone 1. Heating of the air is effected at 3 in any appropriate way: by combustion, burners, etc. It will be observed that combustion or heating is effected in a decelerated air stream just as if the duct were much bigger. Turbulence creating vanes 4 can be disposed upstream of the combustion for improving the heat transfer.

There is thus obtained a thrust increase produced by the increase in the cross-section of the gas passage at the position of the combustion chamber, thereby increasing the combustion area without the frontal area of the machine having been increased. a

According to Figure 2, the hot gases then pass across the second zone of deflection 2 and leave with a velocity V3 parallel to V1 but much greater; this realignment achieves a considerable recuperation of energy.

The application of this arrangement to a thermopropulsive duct is represented schematically in Figure 3; in this figure, 11 is the wall of the duct, 13 is it axis and 15 is, for instance, the pilot cabin or a body of any kind placed in the interior of the duct. The zones of deflection 1 and 2, in this example, are disposed in the form of cones coaxial with the duct.

It is important to note that the second zone of deflection is not indispensable in the reduction to practice of the invention; this second zone serves, in effect, for realignment of the stream lines, which can be achieved automatically or obtained in a different way.

The essential point is the increase of cross-section of the combustion zone by a deflection of the stream lines before their passage into that .zone, by means of a zone of deflection disposed obliquely to the axis.

The second zone of deflection has the further advantage of ensuring a considerable recuperation of energy, and for this reason its utilization is preferred.

While a zone of deflection for the purpose of the invention can be obtained in various ways, this invention primarily provides the use of deflecting blading.

It is known that a profile such as 5 (Fig. 5) set up in such a position as to cause the creation of forces such as Z, is the seat of a circulation 1 which is not zero and=fv the integral being taken around a closed contour enclosing the profile.

A series of such profiles lined up in proper positions is therefore equivalent to a zone of deflection as referred to above.

Fig. 4 represents an embodiment of the invention corresponding to the case of Fig. 1.

According to this figure, a single series of blades 5 is provided; this blading deflects the gas stream through an angle ,82.

Partitions 12 extending the blades 5 are provided and interconnected by turbulence creating vanes 8 disposed normally to the said partitions. The burners are represented at 7, and an ignition means is provided in the same manner as shown in Fig. 2, The position of the vanes Patented Apr. 2, 1957 8, perpendicular to the partitions 12, creates a succession of elementary combustion chambers 13, 14, taggered with respect to one another. The pressures p and p exerted on each face of the same partition, are consequently unequal (p, p and their resultant is a forward force. Ignition means are provided in the same manner as shown at 3 in Fig. 2.

According to Fig. 5, the combustion chamber comprises upstream of the burners 7 a series of deflecting blades 5 set up in proper positions and disposed along an oblique zone With respect to the fluid stream, and downstream of the combustion zone a second series of blades 9 disposed in a zone similarly oblique with respect to the general direction of said stream, and set up in suitable positions so as to straighten it out. The two series of blades form the zones of deflection 1 and a.

Advantageously, vanes 8 are provided to increase the turbulence in the neighborhood of the burners.

It is quite evident that nothing will be modified in the flow of development of heat if the blades situated upstream of the source of heat are connected by walls 10 with those situated downstream of it. Combustion will then take place in true small ducts disposed obliquely in the air stream (see Fig. 6).

The angles a and B are not necessarily constant along This point is important in order to avoid separation in the neighborhood of the walls, downstream of the combustion chamber, without losing the advantages of the invention.

The blades 9 situated downstream of the heat source will be raised to a very high temperature. To ensure that their mechanical properties are not impaired, they, as well as the blades 5, can advantageously be each constituted, as shown by Fig. 7, by a hollow substantially frusto-conical body in which the circulation of fluid will ensure their cooling. They may equally well be covered by a refractory material having a low coeflicient of conductivity.

The invention is not limited to the particularities described and notably not to those illustrated. In particular, any method of creating the zones of deflection can be used without thereby going outside the scope of the invention.

I claim:

1. Propulsion apparatus, comprising, in combination, an elongated duct adapted to convey a combustible fluid axially along the duct in the interior thereof; first turning means located in said duct for turning the fluid flowing along the same inwardly toward the axis of the duct so as to increase the path of flow of the fluid as well as cross-section through which the fluid flows to thereby reduce the speed of flow of the fluid; combustion means located in said duct adjacent to and downstream of said turning means to ignite the fluid; and second turning means located in said duct downstream of said combustion means for turning the fluid back to an axial direction of flow along said duct.

'2. Propulsion apparatus, comprising, in combination, an elongated duct adapted to convey a combustible fluid axially along the duct in the interior thereof; first turning means located in said duct for turning the fluid flowing along the same inwardly toward the axis of the duct so as to increase the path of flow of the fluid as well as the cross-section through which the fluid flows to thereby reduce the speed of flow of the fluid; combustion means located in said duct adjacent to and downstream of said turning means to ignite the fluid; and second turning rmeans located in said duct downstream of said combustion means for turning the :fluid back to an'axial direction of flowalong'saidduct, said first and second turning means being in the form of a plurality of continuous blades having upstream end portions forming said first turning means and downstream end portions forming said second turning means.

3. Propulsion apparatus, comprising, in combination, an elongated duct adapted to convey a combustible fluid axially along the duct in the interior thereof; a plurality of annular substantially frustoconical blades arranged in said duct about the axis thereof and being spaced along said axis with the larger end of each blade located upstream of its smaller end so that said blades form a plurality of annular passage directed inwardly toward the axis of said duct; and a plurality of combustion means located between each pair of said blades respectively in said annular spaces formed thereby and being staggered with respect to each other along the axis of said duct so that the heat produced by said combustion means at one side of .each blade will be cooled by the fluid flowing along the opposite side of each blade.

4. Propulsion apparatus, comprising, in combination, an elongated duct adapted to convey a combustible fluid axially along the duct in the interior thereof; a plurality of annular substantially frustoconical blades arranged in overlapping relationship in said duct about the axis thereof and being spaced along said axi with the larger end of each blade located upstream of its smaller end, the spaces between said blades being free so that said blades form a plurality of frustoconical annular passages directed inwardly toward the axis of the duct, overlapping each other, and being distributed along the axis of the duct; and a plurality of combustion means respectively located in said annular passages.

5. Propulsion apparatus, comprising, in combination, an elongated duct adapted to convey a combustible fluid axially along the duct in the interior thereof; a plurality of annular substantially frustoconical blades arranged in overlapping relationship in said duct about the axis thereof and being spaced along said axis with the larger end of each blade located upstream of its smaller end, the spaces between said blades being free so that said blades form a plurality of frustoconical annular passages directed inwardly toward the axis of the duct, overlapping each other, and being distributed along the axis of the duct, said blades each having adjacent to but spaced from said smaller end thereof an elongated region of a diameter which decreases at a greater rate than the diameter of said blade in the region of said larger end thereof; and a plurality of combustion means respectively located in said annular passages.

6. Propulsion apparatus, comprising, in combination, an elongated duct adapted to convey a combustible fluid axially along the duct in the interior thereof; a plurality of annular substantially frustoconica l blades arranged in overlapping relationship in said duct about the axis thereof and being spaced along said axis with the larger end of each blade located upstream of its smaller end, the spaces between said blades being free so that said blades form a plurality of frustoconical annular passages directed inwardly toward the axis of the duct, overlapping each other, and being distributed along the axis of the duct, said blades each having adjacent to but spaced from said smaller :end thereof an elongated region of a diameter which decreases at a greater rate than the diameter of said blade in the region vof said larger end thereof; and a plurality of combustion means respectively located in said annular passages nearer to said smaller ends of said blades than said larger ends :thereof.

7. Propulsion apparatus, comprising, in combination, an elongated duct adapted to convey a combustible fluid axially along the duct in the interior thereof; a plurality of annular substantially frustoconical blades arranged in overlapping relationship in said duct about the axis thereof .and being spaced along said axis with the larger end of each blade located upstream of its smaller end, the spaces between said blades being free so that said blades form a plurality of frustoconical annular passages directed inwardly toward the axis of the duct, overlapping each other, and being distributed along the axis of the duct, said blades each having adjacent to but spaced from said smaller end thereof an elongated region of a diameter which decreases at a greater rate than the diameter or" said blade adjacent to but spaced from said larger end thereof; a plurality of combustion means respectively located in said annular passages nearer to said smaller ends of said blades than said larger ends thereof; and means for causing a turbulence in the fluid upstream and in the region of said combustion means.

8. Propulsion apparatus as defined in claim 4 and wherein the upstream ends of said blades are located along a surface of revolution whose axis coincides with that of said duct and whose diameter decreases in the downstream direction.

9,. Propulsion apparatus as defined in claim 4 and wherein a means is provided at the downstream ends of said blades, respectively, for directing the fluid at the downstream ends of said blades along a path substantially parallel to the axis of said duct.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,149 Lubbock et al Sept. 20, 1949 1,828,326 Lanser Oct. 20, 1931 2,242,767 Traupel May 20, 1941 2,346,178 Mercier Apr. 11, 1944 2,422,213 Smith June 17, 1947 2,482,505 Pierce Sept. 20, 1949 2,561,005 Wuehr July 17, 1951 2,630,680 Goddard Mar. 10, 1953 

